In dermato-oncology, interferon-alpha is widely used as treatment of cutaneous lymphoma and as adjuvant therapy in high risk malignant melanoma. With increasingly wide administration of interferon-alpha (IFN-alpha), not only early-onset side effects, such as influenza-like symptoms, but also uncommon late-onset side effects are being recognized. We present three patients with melanoma who developed rare side effects in the course of adjuvant IFN-alpha-therapy: sarcoidosis, myasthenia gravis and anterior ischaemic optic neuropathy. Based on current knowledge a causal relationship between these diseases and the administration of IFN-alpha can neither be affirmed or absolutely ruled out. Therefore special attention should be paid to such coincidences.